Kuro no Maou is a Manga/Manhwa/Manhua in english language, Seinen series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

Kurono Mao is a high school student who is sensitive of his sharp eyes and bad expression. No girlfriend but gifted with friends in his own way, he had been living a peaceful life. But one day, without any reason, Kurono was attacked by a mysterious headache while in the literature clubroom and fainted. When he finally awoke....... Swords & magic, filled with monsters, an orthodox different world summoning.